# Slice H-a2 — retained cooldown heartbeat scope

Retail updates item cooldown children from
`UIElement_UIItem::DoHeartbeat @ 0x004E1DF0`. Hidden retained subtrees do not
receive that heartbeat.

The shared acdream controller now keeps the same one-result-per-item heartbeat,
but:

- returns before reading the clock or visiting a slot when the authoritative
  enchantment registry has no cooldown entries;
- visits a mounted `UiItemList` only when the list and every ancestor are
  visible;
- clears the frame's step projection first, so a hidden-only item cannot retain
  a stale ring;
- recomputes the authoritative step on the first heartbeat after the panel
  becomes visible;
- retains existing future-slot and shared-cooldown-group behavior.

Focused tests cover shared groups/future cells, hidden-parent suppression and
reopen, and the zero-work empty-registry path.

Release gate: 3,781 App tests passed / 3 skipped; 8,265 complete-solution
tests passed / 5 skipped.